Wheelchairs often have a fixed seat consisting of a seating surface and a back frame. The seating surface is usually either horizontal or slightly tilted back, with the front edge of the seating surface slightly higher than the rear edge of that surface. If the wheelchair user sits in the same position in a wheelchair for a long period of time, pressure is continuously applied to the tissue on the portion of the user's body (buttocks, legs, and/or back) that is bearing the user's weight in that position. Blood circulation to that tissue will be reduced, and ulcers or other problems can result.
To avoid these problems, it is necessary for people sitting in wheelchairs to shift their body weight from time to time. This is often accomplished by tilting the seat portion of the wheelchair backwards so that the user's weight is shifted away from the pressure points on the user's body. Also, the user's weight can be shifted by reclining the back frame.
It would be advantageous if there could be developed a wheelchair having improved methods for reclining and/or tilting. Further, it would be advantageous if there could be developed improved methods and apparatus for controlling the movement of various movable wheelchair elements such as back frames, seat frames, head rests, arm rests, leg rests and foot rests.